The most common routes for administering pharmaceuticals are oral, intramuscular, subcutaneous, intravenous, and transdermal. Each route has its own particular drawback. For example, a drug administered orally is subjected to harsh conditions including exposure to stomach acids and digestive enzymes even before it gets into the bloodstream via the intestinal tract, hepatic portal system, and liver. The digestive system and first pass metabolism can greatly diminish the activity of the pharmaceutical. As a result, larger doses of the drug are required, leading to undesirable side effects. Despite large drug doses, in many instances the drug may still not reach target tissues such as the brain, head, and neck. The area inside the eye and behind the eye are examples of body areas to which it is difficult to deliver a drug effectively.
Typically, ophthalmic drugs in the form of an eye drop or an ointment are applied to the front of the eye, which is designed to protect the eyes from foreign substances. Drugs administered in this manner do not reach inside or behind the eye. More importantly, other typical drug delivery routes do not allow the drug to induce the desired therapeutic effect at the target gland or tissue.
Injectable drugs enter the circulation immediately but can have undesirable systemic effects.
Transdermal methods of delivery allow the absorption of medicine directly through the skin. Gels, emulsions, creams, sprays and patches are easy to use and are effective for transdermal delivery of a drug. However current transdermal delivery routes are utilized for delivering a drug either to exert a local effect or to enter the blood circulation.
Pharmaceuticals administered by all of the routes described above enter the bloodstream. Additionally, drugs in the circulation cannot always reach all areas of the body. For example, many drugs cannot pass through the blood-brain barrier. It also can be difficult to deliver a drug to an area of the body that is not well vascularized.
The need exists for new routes of drug administration that allow for lower doses to be administered and that allow access of the drug to areas of the body which are difficult to treat, such as the brain, eyes, and other head and neck regions.